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Discovering the causes of cancer and the means of prevention

Current Fellows in the Radiation Epidemiology Branch

Meet the current fellows in the Radiation Epidemiology Branch and learn about research training opportunities.

David Borrego, Ph.D. – Postdoctoral Fellow

David Borrego, Ph.D., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in June 2016. Dr. Borrego earned a B.S. in nuclear and radiological engineering (2010) and both an M.S. (2012) and Ph.D. (2016) in biomedical engineering with a concentration in medical physics from the University of Florida. His doctoral dissertation work focused on assessment of organ doses for fluoroscopically guided interventional procedures. Dr. Borrego’s main research interests are in Monte Carlo estimation of organ doses for patients undergoing radiography and fluoroscopy examinations and organ dose reconstruction based on occupational radiation exposure. In REB, Dr. Borrego is working closely with Choonsik Lee, Ph.D., investigator, REB, Martha Linet, M.D., M.P.H., senior investigator, REB, and Cari Kitahara, Ph.D., M.H.S., investigator, REB, on estimating organ and tissue-specific absorbed doses in members of the U.S. Radiologic Technologist Cohort and for use in epidemiological studies..

Elizabeth (Lisa) Khaykin Cahoon, Ph.D., S.M., M.H.S. – Research Fellow

portrait of Elizabeth Cahoon

Elizabeth Khaykin Cahoon, Ph.D., S.M., M.H.S., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in July 2010. Dr. Cahoon received her master’s in biostatistics in 2005 and her Ph.D. in epidemiology in 2008, both from the Johns Hopkins Bloomberg School of Public Health. Her doctoral research involved examining patient safety in persons with serious mental illness. While at Johns Hopkins, Dr. Cahoon also conducted a meta-analysis on secondhand smoking and cancer for the U.S. Surgeon General’s report on The Health Consequences of Involuntary Exposure to Tobacco Smoke, contributed to writing of The International Agency for Research on Cancer, World Health Organization monograph on secondhand smoking and cancer, and researched the history of radon and cancer. Dr. Cahoon worked under the mentorship of Jonathan Samet, M.D., M.S., Department of Epidemiology Professor and Chair, Gail Daumit, M.D., M.H.S., Associate Professor of Medicine, and William Eaton, Ph.D., Department of Mental Health Professor and Chair during her time at Hopkins. In REB, Dr. Cahoon works with her primary mentor D. Michal Freedman, J.D., M.P.H., Ph.D., epidemiologist, evaluating cancer risks associated with medication use, ultraviolet radiation, and vitamin D in the United States Radiologic Technologists cohort. Dr. Cahoon also works with Kiyohiko Mabuchi, M.D., Dr.P.H., head of the Chernobyl Research Unit and senior scientist, and Alina V. Brenner, M.D., Ph.D., M.P.H., staff scientist on assessment of risks of thyroid cancer and related diseases in cohorts of persons exposed to radiation as a result of the Chernobyl accident.

Scientific Publications - Elizabeth Khaykin Cahoon


Pavel Chernyavskiy, Ph.D. – Postdoctoral Fellow

Pavel Chernyavskiy, Ph.D., started his joint appointment in the Biostatistics Branch (BB) and Radiation Epidemiology Branch (REB) as a postdoctoral fellow in July 2015. He earned a B.S. in economics from SUNY Binghamton in 2007, and both M.S. and Ph.D. in statistics from the University of Nebraska in 2015. For his dissertation research, Dr. Chernyavskiy worked on developing methods for diagnosis and evaluation of traumatic brain injuries in college athletes based on a spatio-temporal model of electroencephalogram (EEG) data collected from the participants. In DCEG, Dr. Chernyavskiy is jointly mentored by Mark Little, D.Phil., senior investigator, REB, and Philip Rosenberg, Ph.D., senior investigator, BB. In REB, he is currently working on large-scale spatial interpolation methods applied to modeling natural background gamma radiation and environmental radiation exposures as they relate to childhood and other cancers. In BB, he is working on extensions of the age-period-cohort (APC) model to account for various types of subgroup heterogeneities in cancer rates, e.g. heterogeneity due to race, cancer registry, and geographic location.

Scientific Publications - Pavel Chernyavskiy

Megan Herr, Ph.D. – Postdoctoral Fellow

Megan Herr, Ph.D., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in October 2015.  She received her Ph.D. in epidemiology from the University of Rochester Medical Center in Rochester, New York in 2015.  Her doctoral dissertation work was focused on antidepressant use and the risk of central nervous system metastasis. Dr. Herr’s research interests include the etiology of second cancers within the setting of hematologic malignancies.  Dr. Herr will be working under the mentorship of Lindsay Morton, Ph.D., senior investigator, REB, on immune-related risk factors for second cancers.

Scientific Publications - Megan Herr

Neige Journy, Ph.D., M.P.H. – Postdoctoral Fellow

portrait of Neige Journey

Neige Journy, Ph.D., M.P.H, joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in March 2015. She received a master’s degree in public health from the Bordeaux School of Public Health, France, prior to completing an M.P.H in biostatistics and Ph.D. in epidemiology from the Paris-Sud University in France. Her doctoral research focused on childhood cancer risks following CT scan exposures. This work was conducted at the French Institute for Nuclear Safety and Radiation Protection under the mentorship of Dr. Marie-Odile Bernier, M.D, M.P.H, and Dr. Dominique Laurier, Ph.D., both of the Laboratory of Epidemiology. In REB, she is involved in studies on cancer risk assessment after diagnostic and therapeutic medical exposures under the mentorship of Dr. Amy Berrington de González, D. Phil., REB Branch Chief.

Scientific Publications - Neige Journy

Gleb Kuzmin, B.S. – Predoctoral Fellow

Gleb Kuzmin, B.S., joined the Radiation Epidemiology Branch (REB) as a predoctoral fellow in August 2015. Mr. Kuzmin received a B.S. in radiation physics from the University of Texas, Austin in May 2013. Currently, he is pursuing his Ph.D. in nuclear engineering with a specialization in health physics at Texas AM University. Throughout his education and research experience, Mr. Kuzmin has worked on various topics in medical physics, including medical dosimetry, computer phantoms, and Monte Carlo simulations. In REB, he is working under the mentorship of Choonsik Lee, Ph.D, investigator, and is focusing on projects related to organ dose reconstruction of proton therapy patients.

Hyeyeun Lim, Ph.D., M.P.H. – Postdoctoral Fellow

Hyeyeun Lim, Ph.D., M.P.H., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in December 2014. Dr. Lim received a B.A. in Health Science from Dongduk Women’s University, South Korea, an M.P.H. in environmental and occupational health science from Emory University (2010), and a Ph.D. in Environmental and Occupational Health from the University of Texas, Houston (2014). For her doctoral work, Dr. Lim evaluated the association between maternal exposure to ionizing radiation during the periconceptional period and selected birth defects in offspring using data from National Birth Defects Prevention Study. In REB, she is working under the mentorship of Martha Linet, M.D., M.P.H., senior investigator, and Cari Kitahara, Ph.D., tenure-track investigator, on evaluating cancer risks associated with diagnostic procedures in the United States Radiologic Technologists Cohort.

Scientific Publications - Hyeyeun Lim

Diana Merino, Ph.D. – Postdoctoral Fellow

Diana Merino, Ph.D, joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in October 2015. In 2009, Dr. Merino received her B.Sc. in honors biology at the University of Waterloo. She earned an M.Sc. in Nutrigenomics in the Department of Human Health and Nutritional Sciences from the University of Guelph, Canada in 2010, and a Ph.D. in cancer genomics through the Department of Medical Biophysics at the University of Toronto in the Genetics and Genome Biology Training Program at the Hospital for Sick Children in 2015. During her master’s training, working under the mentorship of David Mutch, Ph.D., she identified SNPs associated with distinct plasma fatty acid profiles in different ethnic populations of healthy young adults. For her doctoral dissertation research, Dr. Merino refined the molecular landscape of choroid plexus tumors, a set of rare but lethal pediatric brain tumors tightly associated with Li-Fraumeni Syndrome. She conducted integrative microarray, next-generation sequencing, and cross-species genetic analyses to characterize all molecular alterations associated with this type of tumor. Her dissertation work was conducted under the guidance of David Malkin, M.D. In DCEG, Dr. Merino is working with Lindsay Morton, Ph.D., senior investigator, REB, and Sharon Savage, M.D., Chief of the Clinical Genetics Branch, on the genomics of multiple primary tumors. Her work will focus on childhood cancer survivors and individuals with inherited cancer predisposition syndromes, including Li-Fraumeni syndrome.

Scientific Publications - Diana Merino

Arena del Mar Morillo, B.A. – Postbaccalaureate Fellow

Arena del Mar Morillo, B.A., joined the Radiation and Epidemiology Branch in September of 2015 as a postbaccalaureate fellow. Ms. Morillo earned her B.A. in biology with a concentration in political science from Lewis & Clark College in Portland, Oregon in May of 2015. She is working with Lindsay Morton, Ph.D., senior investigator, REB, Ruth Kleinerman, M.P.H., Assistant Chief of REB, and Amy Berrington de Gonzalez, Chief of REB, studying the risk factors and patterns of multiple subsequent childhood cancers, particularly in retinoblastoma. Other interests include genetic counseling, a field in which she intends to specialize.

Matthew Mille, Ph.D. – Postdoctoral Fellow

Matthew Mille, Ph.D., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in January 2016. Dr. Mille received his doctorate in nuclear engineering and science in 2013 from Rensselaer Polytechnic Institute in Troy, New York. Prior to joining REB, Dr. Mille served as a National Research Council postdoctoral associate in the Radiation Physics Division of the National Institute of Standards and Technology (NIST). Dr. Mille’s research centers on computer simulations and metrology related to the delivery, detection, and dosimetry of ionizing radiation in support of important problems in medical imaging, radiation therapy, radiation protection, and homeland security. His research has touched on the need to optimize the radiation dose received by patients undergoing medical imaging exams or radiation treatment for cancer, as well as the need to detect and accurately quantify radioactivity inside the body resulting from planned nuclear medicine procedures or accidental contamination during a radiological emergency.  The key tools of his research are physical and computational human body phantoms, which are used in conjunction with experiments or Monte Carlo radiation transport simulation. In REB, Dr. Mille works with his primary mentor, Choonsik Lee, Ph.D., investigator, to develop tools for performing organ dosimetry in support of retrospective epidemiological studies looking at the risk of second cancers in radiotherapy patients. Dr. Mille is currently exploring the finite-element multigroup discrete ordinates method as an alternative to Monte Carlo for performing dose calculations on large patient cohorts.

Scientific Publications - Matthew Mille

Elizabeth Mosher, B.A. – Postbaccalaureate Fellow

Elizabeth Mosher, B.A., joined the Radiation Epidemiology Branch (REB) as a postbaccalaureate fellow in June 2015. She received her B.A. in mathematics at St. Mary's College of Maryland in 2015. Ms. Mosher was an REB high school intern in 2010 and 2011, working with Choonsik Lee, Ph.D., investigator, REB, on proton therapy research. Currently, Ms. Mosher is working with Dr. Lee on an image-based study of individual variability in the volume and dimensions of the heart. This work will be used to more accurately compute the radiation dose to the heart in retrospective epidemiological studies of cancer risk in radiotherapy patients whose CT images are not available.

Kamau O. Peters, Ph.D., M.P.H. – Postdoctoral Fellow

portrait of Kamau Peters

Kamau O. Peters, Ph.D., M.P.H., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in April 2015.He earned his Ph.D. in environmental health sciences from the Johns Hopkins Bloomberg School of Public Health. Working with Paul T. Strickland, Ph.D., his doctoral research focused on polycyclic aromatic hydrocarbon exposures, inflammation, and asthma exacerbation in children and adults with asthma from Baltimore, Maryland. Dr. Peters earned an M.P.H. in toxicology from the University of Michigan School of Public Health in 2003. He is currently working with Maureen Hatch, Ph.D., staff scientist, REB, and the Chernobyl Research Unit (CRU) of REB to investigate thyroid disease following exposures to fallout from the Chernobyl nuclear power plant accident.

Scientific Publications - Kamau Peters

Van Tran, Ph.D. – Postdoctoral Fellow

Van Tran, Ph.D., joined the Radiation Epidemiology Branch (REB) in August 2015 as a postdoctoral fellow. She earned her Ph.D. in statistics from the University of Rochester Medical Center in New York. Under the mentorship of Dr. Anthony Almudevar, she analyzed gene regulatory networks and proposed an experimental design utilizing a Bayesian framework. Her research interests include graphical networks, measurement error, and longitudinal data analysis. In REB, Dr. Tran is working with Mark Little, D.Phil., senior investigator, REB, Amy Berrington de González, D.Phil., senior investigator and Chief, REB, and Choonsik Lee, Ph.D., investigator, to assess sources of variation in the main parameters determining CT organ dose and to propagate these to uncertainties in cancer risk. She also works with Dr. Peter Inskip, consultant, and Drs. Little and Berrington de González on the analysis of breast cancer in Childhood Cancer Survivor Study (CCSS) data.

Scientific Publications - Van Tran

Raquel Velazquez-Kronen, M.S. – Predoctoral Fellow

Raquel Velazquez-Kronen, M.S., joined the Radiation Epidemiology Branch (REB) as a predoctoral fellow in July 2016. She earned a B.S. in interdisciplinary studies at the University of Central Florida in 2012, and an M.S. in epidemiology in the Department of Epidemiology and Biostatistics from the University at Albany, SUNY (Year). Currently, she is pursuing her Ph.D. in cancer epidemiology at the University at Buffalo, SUNY. During her master’s training, she worked with the New York State Cancer Registry, assessing racial and ethnic disparities in breast and colorectal cancer diagnosis. Raquel was a previous summer fellow at REB. For her doctoral dissertation, she is working under the mentorship of Martha Linet, M.D., M.P.H., senior investigator, and Cari Kitahara, Ph.D., tenure-track investigator, on evaluating cancer risks associated with occupational radiation exposure in the United States Radiologic Technologists Cohort.

Daphnée Villoing, Ph.D. – Postdoctoral Fellow

Daphnee Villoing, Ph.D.

Daphnée Villoing, Ph.D., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in April 2016. Dr. Villoing received an M.Sc. in biomedical engineering (2010), an M.Sc. in medical physics (2011), and a Ph.D. in medical physics (October 2015) from Paul Sabatier University, Toulouse, France.  Her doctoral dissertation work was focused on the impact of the Monte Carlo code GATE on imaging and dosimetric calculations for targeted radionuclide therapy. Dr. Villoing’s main research interests are Monte Carlo modelling, dosimetry of ionizing radiation in medical imaging and radiation therapy, radiation protection, and computational anthropomorphic models for medical imaging and radiation therapy. In REB, Dr. Villoing is working on the calculation of organ doses to patients who underwent diagnostic nuclear medicine procedures between the early 1960s and the present, under the supervision of Choonsik Lee, Ph.D. ,and Vladimir Drozdovitch, Ph.D. She is also involved in the evaluation of historical trends for occupational doses received by participants in the U.S. Radiologic Technologists Study and the U.S. Nuclear Medicine Technologists Pilot Study from 1960-2010, under the supervision of Cari Kitahara, Ph.D. Another component of her postdoctoral work is to estimate uncertainty and to increase dosimetric accuracy for organ doses for patients who underwent nuclear medicine procedures, using Monte Carlo radiation transport coupled with computational human phantoms, under Dr. Lee’s supervision.

Scientific Publications - Daphnée Villoing

Diana Withrow, Ph.D. – Postdoctoral Fellow

Diana Withrow, Ph.D., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in May 2016. Dr. Withrow earned her Ph.D. in epidemiology from the University of Toronto Dalla Lana School of Public Health in 2016. Working with Dr. Loraine Marrett, her doctoral research comprised the first national-level analysis of cancer survival among First Nations and Métis adults in Canada. In 2010, Dr. Withrow earned an M.Sc. in epidemiology from the London School of Hygiene and Tropical Medicine. Dr. Withrow’s research interests include socio-demographic and economic disparities in survival and survivorship, the role of therapy on second cancer risk, and the optimal application of survival analysis techniques to these research areas. At NCI, Dr. Withrow is working with Amy Berrington de González, D.Phil., Branch Chief and senior investigator, REB, and Lindsay Morton, Ph.D., senior investigator, REB. Dr. Withrow is currently working on several projects with the goal of characterizing patterns in second cancer incidence, particularly among breast cancer survivors. 

Scientific Publications - Diana Withrow

Rachel Zamoiski, Ph.D. – Postdoctoral Fellow

Rachel Zamoiski, Ph.D., joined the Radiation Epidemiology Branch (REB) as a postdoctoral fellow in November 2014. Dr. Zamoiski received her Ph.D. in environmental health sciences from the Johns Hopkins Bloomberg School of Public Health (JHSPH) in 2014. Her doctoral dissertation work was focused on studying exposures to heavy metals, vitamin D levels, and inflammation. Dr. Zamoiski also has an M.P.H. from the JHSPH (2007) and a B.A. in Psychology from the University of Pennsylvania (2004). In REB, Dr. Zamoiski is working with Martha Linet, M.D., M.P.H., senior investigator, REB and D. Michal Freedman, J.D., M.P.H., Ph.D., epidemiologist, REB, on cancer risks associated with ultraviolet radiation in the United States Radiologic Technologists Cohort.

Scientific Publications - Rachel Zamoiski

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